Device for short-circuiting two electric lines for reducing a voltage differential

ABSTRACT

A device is for short-circuiting a first electric line with a second electric line in order to reduce a voltage differential. At least one first electronic switching device is provided between the first and second lines and at least one second electronic switching device is arranged anti-parallel to the first switching device. No mechanical switch is present for the direct short-circuiting operation.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE03/00131 which has an Internationalfiling date of Jan. 7, 2003, which designated the United States ofAmerica and which claims priority on German Patent Application number DE102 03 602.0 filed Jan. 30, 2002, the entire contents of which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to a device for short-circuiting a firstelectrical line with a second electrical line for the purpose ofreducing a potential difference or voltage differential. Preferably, atleast one first electronic switching apparatus and, back-to-back inparallel with this, at least one second electronic switching apparatusare arranged between the first and the second line, it being possiblefor a potential difference occurring between the first and the secondelectrical line to be bridged by at least one of the two electronicswitching apparatuses. The first electronic switching apparatuspreferably operates when the potential of the second electrical line isgreater, by a predeterminable differential value, than the potential ofthe first electrical line. Further, the second electronic switchingapparatus preferably operates when the potential of the first electricalline is greater, by a predeterminable differential value, than thepotential of the second electrical line.

BACKGROUND OF THE INVENTION

A known device is disclosed in WO 01/06610 A1. An essential component inthe known device is a mechanical switch which is connected to avoltage-detecting device. The two are each arranged between the twoelectrical lines. When the potential difference, which is detected bythe voltage-detecting device, between the first and the secondelectrical line is too great, the switch is closed, and a short circuitis brought about between the two lines. Only as an addition to themechanical switch are electronic switching units provided which are,however, only intended to supplement the mechanical switch. Themechanical switch containing movable parts essentially brings about thereduction in an undesired potential difference between the first and thesecond line.

Such devices for short-circuiting two electrical lines are often used inrailroad power supply systems. In the case of a DC supply, the firstelectrical line is the rail, which acts as the return line, and thesecond electrical line is the structure ground (ground line).

In the case of isolator flashovers, potential differences between therail and the structure ground may occur which may destroy modules whichare connected to the rails.

SUMMARY OF THE INVENTION

An embodiment of the invention includes an object of specifying a devicefor short-circuiting two electrical lines for the purpose of reducing apotential difference or voltage differential, which is effective largelywithout any movable parts.

An object may be achieved according to an embodiment of the invention byno mechanical switches being provided for direct short-circuitingpurposes.

This is based on the knowledge that the short-circuiting can be reliablymanaged by consistent development of the power semiconductor using thetwo electronic switching apparatuses alone. The aim is to achieve theadvantage of completely avoiding a mechanical switch which tripsrelatively slowly. Nevertheless, this can be done without the need forvery complex electronic components.

For example, each electronic switching apparatus has a component whichchanges from the high-resistance state to the low-resistance state whena fixed voltage is overshot. This component makes it possible toestablish the tolerable differential value of the potentials. Thiscomponent may be a breakover diode, a zener diode or a comparablecomponent.

According to another example, each electronic switching apparatus mayhave an electrical switch which can be operated by a voltage-monitoringdevice arranged between the first and the second line, and which closesimmediately or with a time delay when a threshold value is overshot.

This electrical switch can be arranged, for example, in parallel withthe component of the respective electronic switching apparatus. This maybe, for example, a breakover diode. This provides a staggered effect.

If the direction of flow changes, the electronic switching apparatus isopened again automatically.

In order to allow the electronic switching apparatuses to have a highresistance value again independently of this, a current-detecting devicecan be arranged, for example, between the electronic switchingapparatuses, on the one hand, and one of the two lines, on the otherhand. The current-detecting device may be connected by a control line toa switch in a connecting line between the two lines. The switch servesthe purpose of resetting or cancelling semiconductor switching elementsof the electronic switching apparatus when the switch is closed.

If a non-critical, small current level has now been detected and theelectronic switching apparatus is intended to have a high resistancevalue again, the switch in the connecting line is closed for a shortperiod of time. This switch does not serve the purpose ofshort-circuiting the two electrical lines. It only serves the purpose ofresetting (cancelling) the semiconductor switching elements, in orderfor them always to be capable of functioning reliably.

The electronic switching apparatuses may, for example, also operate witha time delay in order to suppress only potential differences which aretoo great and last for a longer period of time. For this purpose, theelectronic switching apparatuses may contain thyristors which have, forexample, response times of 1 to 2 microseconds.

In one embodiment, the thyristor circuitry includes at least onethyristor, whose cathode is connected to the first electrical line andwhose anode is connected to the second electrical line. A drive circuitis connected to the gate of the thyristor and has a series circuitincluding, for example, a breakover diode, a series starting resistorand a protective diode.

In another embodiment, the thyristor circuitry includes at least onethyristor, whose cathode is connected to the second electrical line andwhose anode is connected to the first electrical line. In this case,too, a drive circuit is connected to the gate of the thyristor and has aseries circuit comprising, for example, a breakover diode, a seriesstarting resistor and a protective diode.

The breakover diode has, for example, a starting voltage of 200 to 800volts.

The device according to an embodiment of the invention has theparticular advantage that two electrical lines can be reliablyshort-circuited, using simple devices/methods/etc. and without anycomplex mechanical switches, for the purpose of reducing a potentialdifference.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention will becomeevident from the description of illustrated exemplary embodiments givenhereinbelow and the accompanying drawings, which are given by way ofillustration only and thus are not limitative of the present invention,wherein:

FIG. 1 shows a device for short-circuiting using breakover diodes.

FIG. 2 shows a device for short-circuiting using a voltage-monitoringdevice and electrical switches.

FIG. 3 shows a combination of the embodiments shown in FIGS. 1 and 2.

FIG. 4 shows the embodiment shown in FIG. 3 which is also equipped witha switch for resetting or cancelling semiconductor switching elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

All of the figures show a first line 1, which may be a rail, and asecond line 2, which may be a ground line. Large potential differencesmay result between the two lines 1 and 2 and need to be compensated forby short-circuiting.

Used for this purpose are two electronic switching apparatuses 3 and 4,the first 3 operating when the potential of the second line 2 is greaterthan the potential of the first line 1, and the second electronicswitching apparatus 4 operating when the potential of the first line 1is greater than the potential of the second line 2. Each of the twoelectronic switching apparatuses 3 and 4 include a thyristor 5, 6 and aseries circuit, arranged in parallel with said thyristor 5, 6, includingfirstly a protective diode 7, 8, which allows current to pass in thesame direction as the thyristor 5, 6, and secondly a current-limitingresistor 9, 10.

According to FIG. 1, each of the series circuits also has a breakoverdiode 11, 12. The breakover diodes 11, 12 are designed such that theyopen when a specific potential is reached at their input. This thereforemakes it possible for the associated thyristor 5, 6 to be switched in amanner that it allows current to pass. The existing semiconductorswitching elements are reset or cancelled when the potential differencebetween the two lines 1 and 2 is zero. This simplest variant of a devicefor short-circuiting two electrical lines 1 and 2 for the purpose ofreducing a potential difference does not use complex electronics or, inparticular, complex mechanical switches.

FIG. 2 shows a variant in which the breakover diodes are replaced byelectrical switches 13, 14. All other components correspond to those ofthe electronic switching apparatuses 3 and 4 which are shown in FIG. 1.These electrical switches 13, 14 close when a specific threshold valuefor the potential difference or voltage differential between the twolines 1 and 2 is reached. In order to be able to detect this potentialdifference, a voltage-monitoring device 15 is arranged between the firstline 1 and the second line 2 and is connected by control lines to theelectrical switches 13 and 14.

An advantage of the embodiment of FIG. 2 as compared with the exemplaryembodiment shown in FIG. 1 is that the threshold value for the potentialdifference, at which an electrical switching apparatus 3 or 4 istriggered, can be varied. The threshold value can be selected bysuitably setting the voltage-monitoring device 15. Different thresholdvalues can therefore be selected for short-circuiting purposes,depending on requirements.

The embodiment shown in FIG. 3 shows a combination of the twoembodiments previously described. In this case, the electrical switches13, 14 known from FIG. 2 are arranged in parallel with the breakoverdiodes 11, 12 known from FIG. 1. The remaining components correspond tothe described embodiments.

The combination of the breakover diode 11, 12 and the electrical switch13, 14 in conjunction with a voltage-monitoring device 15 has anadvantage that the electronic switching apparatuses 3, 4 always respondat the potential differences determined by the breakover diodes 11, 12.In addition, this is true at an even lower potential difference, as longas this potential difference, via the voltage-monitoring device 15,causes the electrical switches 13, 14 to close.

The embodiment shown in FIG. 4 largely corresponds to that shown in FIG.3. In addition, a current-detecting device 16 is arranged between thetwo electronic switching apparatuses 3, 4, on the one hand, and thefirst line 1, on the other hand.

This current-detecting device 16 is arranged via a control line having aswitch 17 in a connecting line 18 between the two lines 1 and 2. Thishas the advantage that the semiconductor switching elements of theelectronic switching apparatuses 3, 4 are reset or cancelled not onlywhen the potential difference between the lines 1 and 2 is zero.

This cancelling may also be triggered even when a small current stillflows through the electronic switching apparatuses 3, 4. In this case,the current-detecting device 16 detects whether the current has fallenbelow a threshold value and then closes, by means of a control line, theswitch 17 acting as the cancel relay.

All of the embodiments according to the invention function without anycomplex mechanical switches for short-circuiting purposes, which wouldhave to be arranged directly between the two lines 1 and 2. In addition,no complex electronics are advantageously required.

Exemplary embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. A device for short-circuiting a first electrical line with a secondelectrical line for reducing a potential difference, comprising: avoltage-monitoring device connected directly between the firstelectrical line and the second electrical line, the voltage-monitoringdevice configured to adjust a threshold value and monitor a potentialdifference between the first electrical line and the second electricalline; at least one first electronic switching apparatus arranged betweenthe first electrical line and the second electrical line; at least onesecond electronic switching apparatus, arranged between the firstelectrical line and the second electrical line and antiparallel to theat least one first electronic switching apparatus, wherein a potentialdifference occurring between the first and the second electrical linesis adapted to be bridged by at least one of the at least one first andsecond electronic switching apparatuses, the at least one firstelectronic switching apparatus operating if the potential of the secondelectrical line is greater, by a predeterminable differential value,than the potential of the first electrical line, and the at least onesecond electronic switching apparatus operating if the potential of thefirst electrical line is greater, by a predeterminable differentialvalue, than the potential of the second electrical line; wherein nomechanical switches are provided for short-circuiting the firstelectrical line to the second electrical line; wherein each of the atleast one first and second electronic switching apparatus includes athyristor and an electrical switch, the electrical switch operable bythe voltage-monitoring device; wherein the electrical switch closes ifthe threshold value is exceeded, the threshold value is variable; andwherein each electrical switch is arranged in parallel with a componentof a respective electronic switching apparatus, the component being oneof a breakover diode and a zener diode.
 2. The device as claimed inclaim 1, wherein the component changes from a high-resistance state to alow-resistance state when a fixed voltage is exceeded.
 3. The device asclaimed in claim 1, further comprising: a current-detecting device witha first end connected between at least one of the first and at least oneof the second electronic switching apparatuses and a second endconnected to one of the first electrical line and the second electricalline, wherein one of the first electrical line and the second electricalline is connected by a control line to a control line switch in aconnecting line between the first electrical line and the secondelectrical line for the purpose of at least one of resetting andcancelling semiconductor switching elements of at least one of the firstand second electronic switching apparatuses when the control line switchis closed.
 4. A device for short-circuiting a first electrical line witha second electrical line, comprising: a voltage-monitoring deviceconnected directly between the first electrical line and the secondelectrical line configured to monitor the potential difference betweenthe first electrical line and the second electrical line; at least onefirst electronic switching apparatus arranged between the first and thesecond electrical lines; and at least one second electronic switchingapparatus arranged between the first and the second electrical lines,wherein mechanical switches are not provided for direct short-circuitingthe first electrical line to the second electrical line, and whereineach of the first and second electronic switching apparatus includes athyristor and an electrical switch operable by the voltage monitoringdevice, and wherein the electrical switch closes if a threshold value isexceeded; wherein each electrical switch is arranged in parallel with acomponent of a respective electronic switching apparatus, the componentbeing one of a breakover diode and a zener diode.
 5. The device asclaimed in claim 4, wherein a potential difference occurring between thefirst and the second electrical line is adapted to be bridged by atleast one of the at least one first and second electronic switchingapparatuses.
 6. The device as claimed in claim 4, wherein the at leastone first electronic switching apparatus operates when the potential ofthe second electrical line is greater, by a differential value, than thepotential of the first electrical line, and the at least one secondelectronic switching apparatus operates when the potential of the firstelectrical line is greater, by a differential value, than the potentialof the second electrical line.
 7. The device as claimed in claim 4,wherein the at least one first electronic switching apparatus operateswhen the potential of the second electrical line is greater, by adifferential value, than the potential of the first electrical line, andthe at least one second electronic switching apparatus operates when thepotential of the first electrical line is greater, by a differentialvalue, than the potential of the second electrical line.
 8. The deviceas claimed in claim 4, wherein the component changes from ahigh-resistance state to a low-resistance state when a fixed voltage isexceeded.
 9. The device as claimed in claim 4, further comprising: acurrent-detecting device with a first end connected between at least oneof the first and at least one of the second electronic switchingapparatuses and one of the first electrical line and the secondelectrical line, wherein one of the first electrical line and the secondelectrical line is connected by a control line to a control line switchin a connecting line between the first electrical line and the secondelectrical line for the purpose of at least one of resetting andcancelling semiconductor switching elements of at least one of the firstand second electronic switching apparatuses when the control line switchis closed.
 10. A device for short-circuiting a first electrical linewith a second electrical line, comprising: at least one first electronicswitching means arranged between the first and the second electricallines; and at least one second electronic switching means arrangedbetween the first and the second electrical lines, at least one of thefirst and second electronic switching means for bridging a potentialdifference occurring between the first and the second electrical line,wherein mechanical switches are not provided for direct short-circuitingthe first electrical line to the second electrical line; wherein thefirst and second electronic switching means are one of reset andcancelled when the potential difference between the first electricalline and second electrical line is zero; a thyristor and electricalswitching means for each of the first and second electronic switchingmeans; and at least one voltage-monitoring means, arranged between thefirst and the second line, for operating the electrical switching means;wherein each electrical switching means is arranged in parallel with acomponent of a respective electronic switching means, the componentbeing one of a breakover diode and a zener diode.
 11. The device asclaimed in claim 10, wherein the at least one first electronic switchingmeans is for operating when the potential of the second electrical lineis greater, by a differential value, than the potential of the firstelectrical line, and the at least one second electronic switching meansis for operating when the potential of the first electrical line isgreater, by a differential value, than the potential of the secondelectrical line.
 12. The device as claimed in claim 10, wherein thecomponent changes from a high-resistance state to a low-resistance statewhen a fixed voltage is exceeded.
 13. The device as claimed in claim 10,further comprising: means for detecting current with a first endconnected between at least one of the first and at least one of thesecond electronic switching apparatuses and a second end connected toone of the first electrical line and second electrical line, wherein oneof the first electrical line and the second electrical line is connectedby a control line to a control line switch means, in a connecting linebetween the first electrical line and the second electrical line, for atleast one of resetting and cancelling semiconductor switching elementsof at least one of the first and second electronic switching means whenthe control line switch means is closed.
 14. The device as claimed inclaim 1, wherein the electrical switch closes if the threshold value isexceeded after a time delay.